Wireless devices, such as cellular phones and tablet devices include one or more antennas. Wireless devices transmit and receive data wirelessly using the antennas. The impedance of an antenna may change, however, under some circumstances. For example, the impedance of an antenna may change based on user proximity to a cellular phone or tablet device. Additionally or alternatively, the impedance of an antenna may change when a user touches a cellular phone or tablet device. Impedance matching for an antenna may also be referred to as antenna tuning.